(1) Field of the Invention
The present invention relates to a sliding bearing for an internal combustion engine in which a pair of semi-cylindrical bearings is combined with each other into a cylindrical shape to support a crankshaft.
(2) Description of the Related Art
Conventionally, a sliding bearing formed into a cylindrical shape by combining two semi-cylindrical bearings is used for a crankshaft. A circumferential oil groove is formed on a bearing inner surface of at least one of a pair of semi-cylindrical bearings, and oil is supplied to an outer circumferential surface of a crankpin via the circumferential oil groove (see JP-A-8-277831).
Meanwhile, in recent years, in order to decrease the leakage amount of lubricant oil from the bearing end portion in response to reduction in size of oil pump for supplying the lubricant oil, it has been proposed to form a narrowed portion in which the sectional area of the oil groove is reduced toward the end portion of the bearing from the bearing central portion, and to remove a crush relief by forming a circumferential oil groove machined by boring on an inner surface of the circumferential end portion of the bearing (see JP-A-2005-69283 and JP-A-2002-188624).
Also, in order to discharge foreign matters accompanying the lubricant oil and entering the sliding surface of the bearing, a bearing is proposed in which a clearance for discharging the foreign matters is formed on the inner surface of the both circumferential end portions of semi-cylindrical bearing (see JP-A-2005-69283 and JP-A-2008-82355).